1. Field of the Invention
The present invention relates generally to equipment for cleaning printing presses. It more particularly relates to equipment for cleaning inking and dampening systems of printing presses.
2. Description of the Prior Art
The typical offset lithographic printing press consists of several main components, namely; a paper feed and deliver system; plate, impression and blanket cylinders; an ink train; a dampening system; and the drive gearing associated with the previously named components. A single printing head consists of all but the feed and delivery systems. Presses have anywhere from one to six printing heads. A particularly laborious aspect of running a press is cleaning the printing heads alter each job. The ink train and dampening is system are the most time consuming to clean. To help better understand why it takes such great effort to clean these systems I will briefly describe the makeup of the typical ink train and dampening systems in use today. After these descriptions I will explain the procedure followed when cleaning the ink train and dampening systems of a press. And finally, the aspects of the cleaning procedure that would be improved through use of the invention described herein will be explained.
Most ink trains are comprised of a chromed ink roller having a doctor blade against its periphery for regulating ink feed, several inking rollers which mill the ink to a thin film, and inking form rollers that evenly distribute the ink film onto a printing plate. Created between the doctor blade and the chromed ink roller is an ink reservoir. Prior to printing a printer will fill this reservoir with the amount of ink needed for the particular printing job. At the end of the job the ink must be removed from the ink reservoir and ink train. An ink blade and washup tray is used for cleaning the ink train.
There are several basic types of dampening systems. A conventional dampening system has one pan roller, usually rotating at less than press speed, picking up the dampening fluid from a dampening fluid pan. The dampening fluid is transferred to a set of dampening rollers by a ductor roller that alternately contacts the pan roller and set of dampener rollers. The set of dampening rollers smooth out the fluid to a consistent thickness and deposit it onto the printing plate prior to the plate passing the inking form rollers, thus, ensuring that the non-image area of the plate stays clear of ink.
Another type of dampening system is a continuos type dampening system. Like the conventional system, this system uses a pan as a reservoir and has a pan roller and a set of dampening rollers. However, instead of the fluid being transferred periodically by a ductor roller, the fluid is transferred directly by a continuously rotating metering roller. Most continuos type dampening systems have a pan roller running at less than press speed, lo therefore, there is a speed differential between at least two, but sometimes several or all of the dampening system rollers.
Both the conventional and continuos type dampening systems require anywhere from 5% to 15% alcohol in the fountain solution to properly wet the plate.
The third type of dampening system consists of only two rollers-a dampening form is roller and a metering roller. Both rollers will usually rotate at press speed. Unlike the conventional and continuos type dampening systems, this third type of dampener does not have a fountain solution pan. Instead, a reservoir of fountain solution is maintained in the nip between the two rollers and a set of end seals.
In regard to dampener system maintenance there are several characteristics inherent to all of the above described dampening systems. First, each system has some type of dampening fluid reservoir that must be drained at the end of the printing operation. In addition, after the fountain solution has been drained from the reservoir, some or all of the rollers of each system must be cleaned of ink with an ink solvent. And, depending on the particular configuration of the dampener, the reservoir must again be drained of spent ink solvent.
Cleaning a single head of a press typically involves the following steps: (1)removing unused ink from the doctor blade/chromed ink roller reservoir and cleaning said blade/roller reservoir by hand, (2)removing unused dampening fluid from the dampening system reservoir, (3)engaging the inker cleanup blade and washup tray against one of the lower inker rollers, (4)applying ink solvent to the inking and dampening rollers, (5)removing the solvent from the washup tray and dampener reservoir after it has reduced and washed away the spent ink from the inking and dampening rollers, and (6)manually wiping down any rollers requiring special attention such as the blanket cylinder, impression cylinder, chromed ink roller, and dampening pan roller.
To apply ink solvent to the inking and dampening rollers as described above in step (4) printers will usually fill a small plastic squeeze bottle with ink solvent and squirt the solvent onto the ink and dampener rollers. Several drawbacks of this method are: a) the squeeze bottle must be refilled frequently, b) the squeeze bottle is not easy to manipulate, and c) the squeeze bottle will more often than not leak ink solvent onto the press operator's hands. There are systems for dispensing ink solvents onto the ink and dampener rollers, however, they tend to be expensive, inflexible, and complicated to operate. An example of such a system is Sarda's apparatus for cleaning and maintaining a printing press, U.S. Pat. No. 5,103,730.
To remove the used fountain solution or spent ink solvent as described above in steps (2) and (5) above the printer must remove the pan or washup tray from the press and dump its contents into a storage container or suction the fluid from the pan or washup tray using a plastic squeeze bottle. Both methods are awkward and often result in spilling the used fountain solution and/or spent ink solvent. There are other types of suction devices used by printers to extract spent fluids from the press, however, they are usually powered by electricity and because of this create a shock hazard to the operator. In addition, since most ink solvents are volatile, use of these devices creates the risk of explosion. Some fountain pans have recirculating systems attached which allow for draining of the fountain solution from the pan to a central fountain solution reservoir after the print job has been completed. An example is Gasparrini's liquid circulating system, U.S. Pat. No. 4,300,450. These systems cannot be used as a drain for the spent ink solvents, however, because the central fountain solution reservoir would become contaminated. Depending on the number of jobs run and the number of printing heads printed on during each job, a printer will be required to clean anywhere from one to eighteen printing heads a day. To clean one head takes approximately ten to fifteen minutes.
From the above is can be understood that the process of cleaning a press takes a considerable amount time and effort. In addition, the process often requires the printer to be exposed to dampening fluids and ink solvents. Any step in the cleaning process that would reduce the time and effort to clean a press and reduce the printers exposure to printing fluids would be of great benefit.
For example, if the time it takes to clean a press could be reduced it would allow more time for printing jobs. This would immediately make the press more economical to run and, thus, make the printer more competitive in the marketplace. Also, if the process of cleaning the press could be simplified to any degree, the printer would experience less fatigue. And because there are many dangers within the printing environment-for example; inward nips, rotating gears and numerous pinching locations-any reduction in operator fatigue would translate to a safer working environment because the printer would remain more alert while operating the press. In addition, because the present method of cleaning a press requires the use of ink solvents and the method of applying these solvents often results in the operator's hands being exposed to the solvents, eliminating exposure would tend to reduce the health risks experienced by a printer.
One area which has received little attention in the past is a quick and convenient apparatus for dispensing ink solvents used to clean the inking and dampening systems and a quick and convenient apparatus for removing used fountain solution and spent ink solvents from the dampening system reservoir and ink washup tray. Such a system would considerably reduce the time it takes to perform three of the six basic steps followed when cleaning a printing press. In addition, it would improve the economics in running a press, reduce fatigue, increase the safety of operating a press, and reduce the health risks associated with handling ink solvents.